In recent years, development of hybrid and electric vehicles equipped with a large-capacity battery to supply electric power to a drive motor mounted as a vehicle drive power source has been prevailing.
An example of battery case mounted on such motor-driven vehicle comprises a tray member holding a battery module including a lithium ion battery, and a cover member covering the tray member. The battery case of this type requires joining the tray member and the cover member together.
For example, patent document 1 discloses a structure for joining the tray member and the cover member together, in which the tray member and the cover member each have a joint portion, the joint portion of the tray member having bolts and nuts embedded therein, so that the tray member and the cover member are fastened together by tightening nuts onto the embedded bolts and tightening bolts into the embedded nuts, from above the joint portion of the cover member.